Colostrum is the thick yellowish fluid produced by mares before their true milk is produced. Literally the difference between life and death for foals, colostrum is loaded with antibodies that fight pathogens until the foal’s own immune system matures. This vital fluid is produced for no more than 24 hours before it is replaced by mare’s milk, which is thinner and white in color. Likewise, the foal’s digestive tract is able to absorb antibodies for only the first 12 to 24 hours after birth, so it is important for the foal to get colostrum from the mare or another source very soon after it is born. Preferably, the foal should nurse within the first two hours after birth and frequently thereafter, ingesting at least 1.5 to 2 liters (up to half a gallon) of colostrum.

Without a mature immune system, foals are at risk for a host of infectious diseases that might require intensive veterinary care to overcome. Even the best treatment may not be effective; unfortunately, infection is the leading cause of death in newborn foals.

Some foals are weak or sick and are unable to nurse, and others that seem to nurse strongly may not get enough colostrum if the mare has been dripping fluid for several days before delivery. If mares drip significant amounts of colostrum before foaling, they can be milked out as needed and the colostrum can be frozen to be given to the foal at birth. To be ready to care for these foals, managers can obtain a supply of frozen colostrum from donor mares. The frozen colostrum should be thawed in warm water rather than in a microwave before bottle-feeding. If the dam has plenty of colostrum but the foal is too weak to stand and nurse, the mare can be milked out and this colostrum can be bottle-fed to the foal. It can also be tube-fed by a veterinarian.

An immunoglobulin (IgG) test can reveal the concentration of antibodies in the foal’s blood. This test should be done in the interval of 12 to 48 hours after birth. If the level is low, the foal can be treated with an intravenous infusion of antibody-rich hyperimmune plasma. Measurement of IgG levels should be part of the routine well-foal examination and should be performed in all foals.

Many owners routinely have the IgG test done on all foals, regardless of nursing behavior or attitude. Foals can look bright and lively and still have low antibody levels, leaving them open to infection. Taking steps to ensure that your foal has adequate immunity in order to decrease the risk of infections early in life is just one of the many steps to be taken during the young equine’s development in order to provide it with the best possible chance at realizing its full athletic potential.